// references/SimplerMutableInteger.java // (c)2021 MindView LLC: see Copyright.txt // We make no guarantees that this code is fit for any purpose. // Visit http://OnJava8.com for more book information. // A trivial wrapper class import java.util.*; import java.util.stream.*; class IntValue2 { public int n; IntValue2(int n) { this.n = n; } } public class SimplerMutableInteger { public static void main(String[] args) { List v = IntStream.range(0, 10) .mapToObj(IntValue2::new) .collect(Collectors.toList()); v.forEach(iv2 -> System.out.print(iv2.n + " ")); System.out.println(); v.forEach(iv2 -> iv2.n += 1); v.forEach(iv2 -> System.out.print(iv2.n + " ")); } } /* Output: 0 1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9 10 */